Solid state illumination sources and optical systems have been extensively used in many applications, such as in bar code readers, optical communication systems, flat image displays, CD and DVD players.
More recently white LEDs and specially designed lenses have found applications for outdoor illumination systems due to significant savings in energy, easiness of mass production or service and much longer life expectancy.
Great efforts in the lens design for LED illumination are required to meet more demanding day to day applications where the shape and the illumination level of the light beam at a remote target have to meet above normal standards and regulations. Both the patent and technical literature provide design and manufacturing solutions for solid state and especially LED remote illumination solutions.
Reference is made in this regard to U.S. Pat. No. 7,009,213 to Camras that teaches an LED based illumination system having a specially designed lens.
Reference is made in this regard to WO 2008/122941 to Montagne that teaches an LED based luminary head to illuminate high aspect ratio rectangular targets such as public roads.
One can distinguish here optical systems for solid state illumination applications where the input beam (IB) from the source and the output beam (OB) coming out from a lens facing the LED have axis that are at least partially collinear and/or parallel.
Reference is made in this regard to U.S. Pat. No. 2,254,961 to Harris, U.S. Pat. No. 5,924,788 to Parkyn and U.S. Pat. No. 6,896,381 to Benitez.
U.S. Pat. No. '381 to Benitez teaches an open optical cavity facing the LED and in the proximity of the LED, this cavity having an axis of revolution and a circular cross section in a plane perpendicular to the incoming light beam from the LED. The optical cavity has a spherical refractive surface that accepts the incoming beam from the LED.
There are also other applications where the input beam (IB) and the output beam (OB) are at an angle calculated to meet certain illumination criteria.
Reference is made in this regard to U.S. Pat. No. 6,607,286 to West, U.S. Pat. No. 6,674,096 to Sommers, U.S. Pat. No. 7,006,306 to Falicoff, U.S. Pat. No. 7,118,236 to Hahm, U.S. Pat. No. 7,153,002 to Kim, U.S. Pat. No. 7,390,117 to Leatherdale, US Patent Application 2007/0257270 to Lu, US Patent Application 2007/0201225 to Holder and EP 1,528,603 to Herbert.
Further reference is made here to commercially available LED based illumination systems produced by companies such as Led Prescriptions Innovators (LPI), Illumination Management Solutions (such as LED LightBARS™), Sekonix, Joliet, Led-Spot Ledil (such as Flare Lens™ and Snow White Lens™).
In U.S. Pat. No. 6,674,096 the lens and the LED source form a single package. In U.S. Pat. No. 7,390,117 to Leatherdale the lens and the source LED die are separated. In U.S. Pat. No. 6,607,286 to West an optical cavity having an axis of revolution and a circular shape in cross section covers and encapsulates the LED die. Contrary to West '286 in U.S. Pat. No. 7,153,002 to Kim the lens has an optical cavity remote from the LED and fully enclosed in the lens body. This cavity provides both reflective and refractive surfaces to direct the beam towards a direction to a target that is angled from an axis that is normal to the LED die. U.S. Pat. No. 5,926,320 to Parkyn also teaches an enclosed air gap cavity
In most cases disclosed in patent literature the lenses used in conjunction with solid state light sources, such as LEDs, have a circular perimeter having an axis of reference going through the LED die. Such a circular perimeter lenses are used in street illumination, such as in FIGS. 21-26 of US 20070201225 to Holder. FIGS. 21-25 of Holder '225 show a composite lens having several sub-lenses, each having a “blob” or a dome shaped lens portions. This portion can be seen as a sub-lenses that generate several illumination beams upon a target, such as a street. WO 2008122941 to Montagne shows a two lobs LED lens for street illumination where each lob has a circular parameter U.S. Pat. No. 7,390,117 to Leatherdale teaches several designs where the LED lens has a single body that has a polygonal perimeter, these lenses being made of two optical materials for use in lateral illumination.
There is a need to further improve the solid state illumination systems for applications where the energy and the shape of the light beams at the level of a target meet increased demanding criteria without complicating the design of the lens or making them more complicated.